Well, I wouldn't rule the idea out, if you look around on his homepage(the link is on his pixiv profile) then you'll see the artist draws a lot of Code Geass fanart, including doujin work.
I've seen people on pixiv not really tagging things properly when they already have posted said item on their blog. The signature on this pic seems to indicate it was drawn in 2007. So maybe it was intended as a Cosplay/Parody afterall?
Eh. Just looks like Sailor Mars cribbing a pose from Geass, and that's more a style thing than a parody or direct reference. I don't think it's tag-worthy.
